The thesis addresses the impact of androgen deprivation in combination with gene functions in prostate cancer (PCa), as well as the development of ex vivo cancer models. The studies extended to assess of drug efficacies that may employed in future strategies for precision therapies in PCa. The patient-derived-cells (PDCs) from kidney cancer or renal cell carcinoma (RCC) patients further provided opportunities to study clonal evolution pathways, and to evaluate, how the intra-tumor heterogeneity may influence drug resistance at subclonal level.
The biology of PCa revolves around androgen receptor (AR) signaling, thus, it remains the key target for therapeutic strategies. However, development of combinatorial therapies is of critical importance, since targeting AR alone is not enough for long-term benefits of patients. The two projects in the thesis address different avenues of finding novel treatment strategies for PCa.
In the first project, RNA interference (RNAi) screens with 2068 human genes, was design to understand the combinatorial impact of individual gene functions and environmental challenges posed by androgen depletion in PCa. The screen identified several known genes, as well as novel ones, such as HSPBAP1, that inhibited proliferation exclusively in androgen-deprived PCa cells. HSPBAP1 was found to interact with AR in the cell nuclei, and its inhibition led to reduced AR-mediated transcription. The data suggested that the AR-interacting protein HSPBAP1 could be a potential target for intervention in combination with androgen-deprivation in PCa cells.
Our second approach to discover treatment avenues for PCa was to generate novel PCa cell models from patient-derived material for ex vivo evaluation of drug efficacies. The PDCs from PCa patients displayed an AR-negative predominantly basal/transit-amplifying phenotype. The cancer culture retained cancer-specific copy number changes and exhibited a distinct drug response when profiled with 306 oncology compounds. The drugs included taxanes, bexarotene, tretinoin, oxaliplatin, mepacrine and navitoclax function independently of AR signaling, and most of these have already been explored in clinical trials for treating advanced PCa.
Next, we took the strategy applied in PCa to RCC. Since RCC is well-recognized to be genetically heterogeneous disease, we explored the impact of intra-tumor heterogeneity and clonal evolution on drug efficacies based on multiple PDCs generated from the patients. The PDCs were sensitive to established drugs already applied in clinical practice for RCC treatment, such as the mTOR-inhibitor temsirolimus and multi-kinase-inhibitor pazopanib. The individual PDC models from the same patient exhibited diverse drug response patterns suggesting that clonal evolution of cancer directly contributes to differences in drug response. Furthermore, cure in advanced RCC will depend on the design of combinatorial treatments that block each such clone.
In summary, in our first project on RNAi-based functional screening in PCa, we established that knockdown of the HSPBAP1 gene will synergize with androgen-depletion in inhibiting PCa cell growth. We then generated comprehensive drug sensitivity testing (DST) on ex vivo models of prostate and renal cancer cells with the aim to discover additional treatment options. DST profiles measured from patient-specific cancer models could in the future pave the way for exploring new indications for existing drugs, to prioritize drug leads and to allocate individualized therapies to cancer patients.The thesis addresses the future therapeutic strategies in prostate and Kidney/renal cancer. The two projects in the thesis address different avenues of finding novel treatment strategies for prostate cancer (PCa). The first project was design to understand the combinatorial impact of individual gene functions and environmental challenges posed by androgen depletion. To this end, an RNA interference (RNAi) screen targeting 2068 human genes was designed that identified genes whose knockdown inhibited proliferation of PCa cells exclusively in androgen-deprived conditions. HSPBAP1 was one of such gene that was further investigated for its role in the prospective of androgen receptor (AR)/androgen signaling in PCa. The data suggested that survival of androgen dependent cancer cells can be inhibited by the simultaneous inhibition of androgens and novel AR-interacting protein HSPBAP1 (Study I).
The second project was dedicated to establish patient-derived models from PCa patients-derived tissues to pilot drug sensitivity profiling in combination with molecular characterization. The results emphasize the value of newly generated cancer model cell lines along with clinical data and molecular profiling for the study of disease mechanisms, biomarkers and associated drug sensitivity (Study II).
To evaluate the impact of tumor heterogeneity and clonal evolution in cancer, we developed multiple PDCs from renal cancer (RCC) patients. The individual PDC models from the same patient exhibited diverse drug response patterns suggesting that clonal evolution of cancer directly contributes to variabilities in drug response. The study highlighted the impact of intra-tumor heterogeneity, explored pharmacogenomics associations to define combinatorial treatments needed to target multiple subclones present in cancer (Study III).
The application of these ex vivo cultures for functional testing and molecular profiling has the potential to provide tools for drug discoveries and development. This would have implications for cancer diagnosis, tailoring of drugs, designing of effective drug combinations and for future precision system medicine.